PLATE HEAT EXCHANGER

Abstract: In a plate heat exchanger (2) comprising a stack of plates (4) pressed together to define flow spaces (24) between pairs of adjacent plates, the stack being compressed together between a head (10) and a follower (14) by means of load bearing rails (6, 8), the head (10) and the follower (14) are urged together by tie bars (16). To obtain even compression of the plates (4) the tie bars (16) are as close as possible to the flow spaces (24). In one embodiment, at least one tie bar (16) extends through a cut-out (15a) formed within a plate area, the cut-out being bounded at the outer periphery of one of the plates.

Description: PLATE HEAT EXCHANGER The present invention relates to a plate heat exchanger. Plate heat exchangers comprise a stack of plates which are pressed together to define flow spaces between pairs of adjacent plates. Heat exchange media flow through alternate spaces and are in heat exchange via the intervening plate. Typically, adjacent plates are sealed together by an elastometic gasket which sits in a channel in one or both of the plates. Some or all of the plates may be welded of brazed together, and a metal gasket may be used. The heat exchange media are often fed through the heat exchanger under pressure. Consequently, there is a need to compress the plates together and retain this compression under pressure. This is achieved by clamping the stack of plates in a frame between a head and a follower which are urged together by tie bars. In some known designs the tie bars are located adjacent and to each side of cut-outs in the upper and lower edges of the plates, the cut-outs being used to locate the plates on upper and lower rails. US-A-4 813 478 shows a system in which a tie bar is placed at each of the top and bottom edges of the frame, off-set to opposite sides of a vertical centre-line. Tie bars are also provided on each side, off-set vertically relative to one another. However, even compression of the stack of plates is best achieved when the tie bars are as close as possible to the flow spaces between the plates. According to the present invention in a plate heat exchanger comprising a stack of plates which are compressed together between a head and a follower by means of a tie bar, the tie bar extends through a cut-out or aperture formed within a plate area bounded by the outer periphery of at least one of the plates in the stack. The plates may have upper and lower cut-outs or apertures which locate the plates between top and bottom rails, and the cut-out or aperture through which the tie bar extends is one of the said upper and lower cut-outs or apertures. Preferably two bars are provided, the tie bars extending respectively through the upper and lower cut-outs of apertures in the plate or plates. Other tie bars may be provided in other locations if desired. By positioning a tie bar in a cut-out or aperture, which is usually on the centre-line of the plate, even compression of the stack can be achieved, and only a simple modification to the design of the cut-out is required, if at all. In a preferred embodiment, a rail is tubular and a tie bar extends through the rail. In another embodiment, at least one tie bar extends through the flow space and is separated from the flow space by a seal. Other preferred features and advantages of the invention will be apparent from the following description and the accompanying claims. The invention will be further described by way of example with reference to the accompanying drawings, in which: Figure 1 is a schematic side view of a plate heat exchanger; Figure 2 is a plan view of a plate of the plate heat exchanger of Figure 1 along the line II-II; Figure 3 is a plan view of a follower of the heat exchanger of Figure 1, along the line III-III; Figure 4 is a detail from a plate of a heat exchanger of the type seen in Figure 1, and illustrating a first embodiment of the invention; Figure 5 illustrates a second embodiment of the invention; and Figure 6 illustrates a third embodiment of the invention. Figure 7 illustrates a fourth embodiment of the invention. Referring to Figure 1, this shows in side view a schematic illustration of a typical plate heat exchanger 2. The heat exchanger 2 consists of a pack of plates 4 held in a frame 5. The plates 4 are suspended from a top rail 6 and located by a bottom rail 8 extending between a head 10 and an end support 12. The plates 4 are pressed together between the head 10 and a follower 14 which is movable along the top and bottom rails 6, 8. The pack of plates 4 is retained in compressed condition by tie bars 16 which extend between the head 10 and follower 14. Usually, the tie bars 16 are even in number and are located evenly on each side of the stack of plates 4, as seen in Figure 3. Adjacent plates 4 are sealed together, usually by gaskets, to define spaces between the plates. The media are in heat exchange flow through alternate spaces and are in heat exchange contact through the intervening plates. Fluid connections 18 (usually four in number) are provided on the head 10 for feeding the media to and from the pack of plates . As seen in Figure 2, which shows a schematic view of a plate 4, the plate 4 has inlet and outlet ports 20a, 20b which are surrounded by a gasket 22 which defines a flow space 24 in communication with the ports 20a, 20b. The flow space 24 is defined between the plate 4 shown, the gasket 22 and another complementary plate 4 in front of the plane of the drawing. Ports 21a, 21b in the plate 4 are isolated from the flow space 24 by the gasket 22, the ports 21a, 21b and feed a second fluid through to an adjacent flow space defined behind the plate 4. A out-out in upper edge 23a of the plate 4 forms a hanging eye 25 which embraces the top rail 6 and a second cut-out in the lower edge 23b of the plate 4 forms a guide eye 26 which sits over the bottom rail 8. The top rail 6 has a bifurcation 28 at its lower edge, the bifurcation extending along the length of the rail 6. It can be seen that the outer perimeter 34 of the plate 4 defines a plate area bound by the chain-dotted line, the cut-outs 25, 26 extending into the plate area. As seen in Figure 3, the follower 14 is similarly provided with a hanging eye 29 and a guide eye 30, and in addition has apertures 31 for receiving the tie bars 16, the tie bars extending alongside the stack of plates 4. Placing the tie bars to each side of the stack of plates is convenient, but is not always the most efficient solution. It is also known to place the tie bars to one or both sides of the hanging eyes 25, 29 in the head 10 and follower 14, but displaced vertically to be clear of the plates. Figure 4 shows a first embodiment of the invention, in which a plate 4a is constructed generally as seem in Figure 2, a stack of the plates 4a being assembled together to form a plate heat exchanger as seen in Figure 1. In this embodiment, a tie bar 16 extends through the hanging eye 25a. Conveniently, the tie bar 16 is positioned near and below the hanging rail bifurcation 28. The hanging eye 25a may be enlarged downwardly compared to the Figure 2 arrangement, to provide room for the tie bar 16. It can be seen from Figure 2 that the usual plate design provides space for enlargement of the hanging eye in this direction without encroaching on the flow space 24. The corresponding follower (not shown) may have an eye shaped to receive snugly the tie bar 16, so that a tightening nut can bear on the follower, or a tommy bar, washer plate, or other means may be provided. Figure 5 shows a second embodiment of the invention, in which a tie bar 16 is positioned in the lower guide eye 26a. The guide eye 26a may be extended upwardly if necessary to accommodate the tie bar 16 without encroaching on the flow space. The guide rail 8 may be another cross-sectional shape, such as square, to offer greater space for the tie bar 16. Figure 6 shows a third embodiment of the invention, in which a tie bar 16 passes through the bottom rail 8a, the rail 8a being hollow, and telescoped or compressible to allow tightening of the tie bar 16 against the follower. Figure 7 shows a fourth embodiment in which at least one tie bar 16 passes through apertures 32 in the plates 4d, in a position surrounded by the flow spaces 24a and separated thereform by a seal 34, such as for example a metal or an elastomeric gasket, or a welded or brazed seal. It will be appreciated that a tie bar 16 may be wholly positioned, when viewed in cross-section, within a cut-out, or it may protrude outside of the cut-out and hence outside of the plate area. It is particularly preferred to use, for the tie bars, cut-outs or apertures on the vertical centre line of the plates . Various modifications may be made to the embodiments of the invention and it is desired to include all such modifications as fall within the scope of the accompanying claims.

Claims: CLAIMS 1. A plate heat exchanger comprising a stack of plates which are compressed together between a head and a follower by means of load bearing rails in which at least one tie bar extends through a cut-out formed within a plate area, the cut-out being bounded by the outer periphery of at least one of the plates. 2. A plate heat exchanger comprising a stack of plates which are compressed together between a head and a follower by means of load bearing rails at least one tie bar extending through a cut-out formed within a plate area, the cut-out being bounded by the outer periphery of at least one of the plates, in which the plates have upper and lower cut-outs which locate the plates between top and bottom rails, and the cut-out through which the tie bar extends is one of the said upper and lower cut-outs. 3. A plate heat exchanger as claimed in claim 2, wherein a first tie bar extends through the upper cut-outs of the plates and a second tie bar extends through the lower cut-outs of the plates. 4. A plate heat exchanger as claimed in claim 2 or 3, wherein the tie bar is positioned in the upper cut-outs, below the top rail. 5. A plate heat exchanger as claimed in claim 4, wherein the top rail is bifurcated at its lower edge, and the tie bar is positioned in the crotch of the bifurcation. 6. A plate heat exchanger as claimed in any one of claims 2 to 5, wherein the or a tie bar extends through the lower cut-outs and is positioned above the bottom rail. 7. A plate heat exchanger as claimed in any one of claims 1 to 6, wherein one of the rails is tubular and a tie bar extends through the one of the rails. 8. A plate heat exchanger comprising a stack of plates which are compressed together between a head and a follower by means of load bearing rails in which at least one tie bar extends through an aperture formed within a plate area, wherein the tie bar extends through an aperture in the body of the plate so as to penetrate the plates in a region surrounded by the flow spaces between the plates, the aperture being sealed from the flow spaces by a seal. 9. A plate heat exchanger as claimed in any preceding claim in which the tie bar is located on the vertical centre line of the heat exchanger. 10. A plate heat exchanger substantially as described herein with reference to and as illustrated in Figure 4 of the accompanying drawings. 11. A plate heat exchanger substantially as described herein with reference to and as illustrated in Figure 5 of the accompanying drawings. 12. A plate heat exchanger substantially as described herein with reference to and as illustrated in Figure 6 of the accompanying drawings. 13. A plate heat exchanger substantially as described herein with reference to and as illustrated in Figure 7 of the accompanying drawings. 14. A plate for a heat exchanger as defined in any one of claims 1 to 9. 15. A heat exchanger plate having a cut-out or aperture for receiving a rail for locating the plate, wherein the cut-out or aperture is adapted to receive a tie bar. 16. A heat exchanger plate having a cut-out or aperture whose purpose is to locate the plate on a rail and to accommodate a tie bar.

Inventors: FINCH DEREK IAN, FINCH, DEREK, IAN
Applicants: APV CORP LTD, FINCH DEREK IAN, APV CORPORATION LIMITED, FINCH, DEREK, IAN
Application year: 1994
Main classification: F28F3
IPC codes: F28F3